Bulletins will be sent free upon application to Experiment StatioA,
GAINESVILLE, FLORIDA

ACKNOWLEDGMENTS

For many valuable suggestions in regard to the summer-fal-
low method, the writer is indebted to Dr. C. D. Sherbakoff,
former associate pathologist of the Florida Experiment Station.
Figures 11 and 12 are from photographs taken by A. H. Beyer,
assistant entomologist of the Florida Experiment Station.

BUNCH VELVET BEANS TO CONTROL
ROOT-KNOT
A year ago in Bulletin 159 the writer published a preliminary
report on the control of root-knot by the growing of velvet beans
on infested land. Further experiments since that time, partic-
ularly with bunch velvet beans, have given some very striking
results.
Altho these experiments with bunch velvet beans are far from
complete and are being continued on a larger scale and in several
parts of the state, the degree of control already obtained is so
striking and the interests involved so great that we do not feel
justified in withholding the information from the farmers for
another year while further experiments are being carried on.
In this bulletin only this new method of controlling nematodes
is discussed. For other methods of controlling nematodes, list
of susceptible plants, etc., see Bulletin 159, Florida Agricultural
Experiment Station.

THE SUMMER FALLOW
This method of controlling nematodes has grown out of the
summer-fallow experiments which were started by this station
several years ago. By keeping land entirely free of vegetation
all summer, which can be done by frequent cultivations, and by
not allowing any crust to form on its surface, it was found that
the number of root-knot nematodes in the soil could be greatly
reduced.
This method is based on the study of the. fundamental re-
quirements of the nematode worms which cause root-knot. In
order to grow, these worms must have an ample supply of three
essentials. These are, first, a certain amount of heat; second, an
abundance of soil moisture; and third, plenty of air, If any one
of these three essentials are lacking, the worms go into a rest-
ing stage, form a thick wall about themselves and lie dormant
until all essentials are again present. This act is known as
encysting. But when all three of these essentials are present,
the nematodes live and their eggs must hatch.
During summer in Florida there is plenty of moisture and
heat in the soil, but frequent rains often form a crust over the
soil by packing the surface. This crust prevents the entrance
of sufficient air, and thus eliminates one of the essentials. Under

56 Florida Agricultural Experiment Station

these conditions nematode eggs will not hatch. Frequent culti-
vation breaks this crust of soil and allows the air to enter.
With all three essentials, again present, the eggs hatch. Fre-
quent cultivation has prevented the growth of plants and now
the newly hatched worms, having nothing to feed upon, die.
Accordingly, in these summer-fallow experiments the soil was
kept constantly stirred thruout the summer. It was cultivated
at least once a week and after every heavy rain, a crust which
might exclude air was never allowed to remain on the soil. The
results recorded in Bulletin 159, concerning the control of nema-
todes, were quite satisfactory.
However, this summer-fallow method is objectionable, because
it greatly impoverishes the soil. The hot sun and heavy rains
of summer destroy not only the humus in the soil but also the
bacteria and other soil organisms, leaving the soil extremely
poor in both plant food and living matter. The soil, in other
words, is "dead."

VELVET BEANS UNDER CONSTANT CULTIVATION

In an attempt to find some method which will control root-
knot as well as does the summer-fallow method and which at
the same time will not possess the great objection of that method,
the cultivation of velvet beans on the land was tried. The beans
were planted in rows and it was endeavored to maintain the same
constant cultivation as with the summer fallow in order to keep
the land free of weeds. The ordinary running velvet bean was
used at first, but its cultivation was found impracticable after
the vines commenced to run. They formed such a tangled mass
that cultivation became well nigh impossible and it was very
difficult to detect all weeds in the field. With the advent of the
bush velvet bean it was substituted for the running varieties
and has proved much better for the purpose of the experiment.
Constant cultivation is possible with this plant and it is much
easier to see weeds in the field. A plot was planted to these
beans in May, 1921, and cultivated until November. For com-
parison another plot was planted to Brabham cowpeas, another
to Whippoorwill cowpeas and on still another a summer fallow
was maintained.
During winter susceptible truck crops were grown on this
land in order to test the degree of nematode control obtained.
This-the planting of susceptible crops and then inspecting their

Bulletin 163, Bunch Velvet Beans 57

roots for nematode galls-is the usual method practiced in these
experiments of testing the soil for the presence of nematodes.
To attempt to find the worms themselves in the soil would be
like looking for a needle in a haystack.
The degree of control obtained with the bunch velvet bean
much exceeded all expectations. In a recently completed test,
conducted for the purpose of determining the presence of nema-
todes, a very satisfactory crop of snap beans was raised on land
that a year ago was too heavily infested to grow them. (Fig.
11.) Snap bean crops grown upon check plots, which had pre-
viously grown cowpeas instead of bunch velvet beans, were al-
most complete failures. (See fig. 12.)
The method differs from the ordinary one of planting velvet
beans in a field in that constant cultivation is insisted upon and
absolutely all weeds must be kept out of the field-the crop is
never "laid by."
For use in nematode or root-knot control the bunch velvet
bean has two advantages over the ordinary running beans.
First, it allows constant cultivation. Running beans make cul-
tivation impossible during the latter part of the season at least.
Second, their growing season is shorter than that of the ordinary
Florida velvet bean. This makes it particularly valuable to the
trucker, as the period when the land is not in use is too short for
the growing of a crop of ordinary Florida velvet beans. Velvet
beans are practically immune to root-knot. This is not true of any
variety of cowpeas, altho the Iron, Brabham and Victory are
highly resistant.
It is felt that this is the most economical method of ridding
truck lands of nematodes. The experience of the last two years
at this station indicates that one summer is sufficient to reduce
the number of nematodes to the point where a crop of susceptible
plants can be grown on the land. But in order to reduce them
to this point, cultivation must be frequent, at least once a week,
certainly after every rain which packs the soil. All weeds must
be kept out of the velvet beans by occasional hoeings; otherwise
some of the weeds would act as host plants for the nematodes,
and thus carry them over and defeat the purpose of the summer-
fallow treatment.
In order to shade the land satisfactorily, bush velvet beans
should be planted much thicker than running varieties, in fact,
almost as thick as cowpeas. The rows should be not over three

58 Florida Agricultural Experiment Station

and one-half (31/2) feet apart and the beans not less than 18
inches apart in the row. To insure a good stand plant consid-
erably thicker than this. If plowed under in the fall, the beans
will add a large amount of humus to the soil and leave it much
richer in plant food. These are additional benefits to be derived
from the growing of bunch velvet beans (a legume) which
should not be overlooked.
Altho the labor of cultivating and hoeing the beans thruout
summer is no small item, it is an expense well worth making,
if the truck land is seriously infested with nematodes. Further-
more, by practicing this method one avoids the expense of clear-
ing the land in fall, a necessary operation when the land is al-.
lowed to lie out all summer and to grow a heavy crop of weeds
and grass. The labor of clearing such land frequently will be
as great as the expense of cultivating the crop of velvet beans.

Fig. 12.-The land here was treated similar to that shown in figure 11,
except that cowpeas were grown instead of bunch velvet beans and
the surface soil was not kept mulched. Note that this bean crop is
a hopeless failure

Velvet beans should be planted as early as possible after the
last spring truck crop has been removed, by June if possible.
To plant in May is even better.
If desired, one can plant corn in the bean rows, and thus get
an additional return for his labor. However, corn is not always
,absolutely immune to root-knot, but usually is resistant enough
to interfere but little in destroying the nematodes.

Bulletin 163, Bunch Velvet Beans 59

We strongly recommend to truckers that they employ this
method during summer on land infested with root-knot.
This method of treating land has given as satisfactory results
as the old method of growing resistant plants on the land for
two or three years, and has the great advantage of the trucker's
being able to use his land continuously, not losing one or two
trucking seasons.

THE VELVET BEAN CATERPILLAR

Like all velvet beans the bunch variety is likely to be attacked
in August and September by the velvet bean caterpillar. Indeed,
our experience during the past two years indicates that to this
moth the bunch is one of the most attractive varieties of the
velvet bean. This insect works up each year from the south,
arriving earlier and being most destructive in the southern-most
counties.
Truckers growing velvet beans by the summer-fallow method
to control root-knot, must be prepared to combat this cater-
pillar. This is done best by dusting the plants with a mixture
of equal parts of lead-arsenate powder and air-slacked lime. Vel-
vet beans are burned easily by arsenicals; therefore, only the
best grade of lead arsenate should be used, and the lime must
be air-slacked perfectly. Do not use paris green or calcium
arsenate on velvet beans. To get an even distribution of the
powder, a dusting machine is essential. A hand duster that will
do the work can be purchased for about $15.
For further details and illustrations of this caterpillar see
Bulletin 130, Florida Experiment Station.